(1) Field of the Invention
The present invention relates to an improved interlock assembly for preventing more than one drawer in a cabinet from being opened at one time. In particular, the present invention relates to an interlock assembly comprised of a train of drawer interlock units having horizontally rotating cam members with opposed cam surfaces which contact block members having mating cam surfaces. The cam members pivot with respect to the block members around a longitudinal axis of the train of interlock units while a configuration of mating male pins and female openings in the block members and cam member retains the individual interlock units together, along the longitudinal axis. The cam surfaces on the cam members and the block members comprise sinusoidal lobes and valleys that mate together when the interlock assembly is in a rest position when no drawers are open. Opening a first drawer, causes the cam member corresponding to the first drawer to pivot around the axis so that the lobes of the cam member are rotated to seat in indentations in the lobes of the block members. This causes the train of interlock units to move along the longitudinal axis to contact opposed walls in the cabinet, thereby preventing a second drawer from being opened. The block members have tab portions extending from one side of the block members. The block members are mounted in a guide channel that extends the length of the train of interlock units. A portion of the guide channel extends around the tab portion of the block members. The guide channel thus prevents the block members from rotating around the longitudinal axis of the train of interlock units while enabling the block members to move linearly along the longitudinal axis when a cam member is pivoted by opening a drawer. That way, the cabinet is prevented from becoming top heavy and tipping over. The interlock assembly also acts as a safety device by preventing a person bent over a lower drawer from hitting their head on an opened upper drawer.
(2) Prior Art
U.S. Pat. No. 4,480,883 to Young describes an interlock assembly wherein cam elements rotate vertically to raise and lower vertically mounted locking bars provided in a track. The device works well; however, the interlock mechanism is quite expensive to manufacture and assemble. U.S. Pat. No. 4,298,236 to Laroche also describes cam elements which are vertically rotated to move locking bars. This apparatus is more expensive to construct than the present invention.
U.S. Pat. No. 4,732,434 to Hartrum describes an interlock assembly for a cabinet wherein a train of drawer interlock units having horizontally rotating cam members with mating block members corresponding to the drawers in the cabinet slide on a rod mounted between opposed walls in the cabinet. The cam members and block members have sinusoidal surfaces with lobes and valleys that mate when the drawers are closed. When a first drawer is opened, the corresponding cam member is rotated on the rod to cause the lobes to seat in indentations in the lobes of the block members. This causes the block members of the rotated cam member and the remaining units of block and cam members to move on the rod to contact the opposed walls in the cabinet so that a second drawer can not be opened. This device works well; however, there is a need for an improved interlock assembly that is less difficult and expensive to construct and which is easily retrofitted to existing file cabinets.
Other prior art believed to be less pertinent is described in U.S. Pat. Nos. 4,355,851 to Slusser and 3,909,090 to Breckner et al.